Choice, decision and action
investigated with visually guided
saccades.
Jeffrey D. Schall
With
Leanne Boucher, Gordon Logan & Tom Palmeri
NEUROBIOLOGY OF DECISION-MAKING, CSHL, May 2005
Definitions
• Choice – action in the context of alternatives to satisfy a goal,
desire or preference
• Action – movements with consequences that can be explained
by referring to preferences, goals and beliefs
• Decision – deliberation when alternatives are vague, payoffs are
unclear and habits are reversed
"I feel that way right now. Ask me in two or three
months and I may change. I don't think I will. I'm
pretty sure that's my decision."
— Michael Jordan on his retirement from
professional basketball. Associated Press, 17 July
1998.
“I look forward to playing and hopefully I can get to
that point where I can make that decision.”
— Michael Jordan on his anticipated return to
professional basketball. Associated Press, 19 July
2001.
Further defining “decision”
• Distinguish two uses of “decision”
• As characteristic of behavior (e.g., Decision Theory)
• But measures of outcome do not specify mechanism
• As process producing behavior
• Mechanism with particular architecture
• Decision as process has two distinct meanings
• Decide to -- Alternative actions (can be identified with
choosing)
• Decide that -- Alternative categories (not identified with
choosing)
Necessity of formal linking propositions
• The properties of neurons do not reveal function
• Formal (computational) theories of performance explain function
• But distinct models cannot be distinguished from behavior testing,
e.g., diffusion or race
• Properties of neurons might provide constraints to distinguish
between models …
• … if and only if the neural activity measured is the instantiation of
the cognitive process in question, which constitutes a linking
proposition
Teller DY. 1984. Vision Research 24:1233-1246
Schall JD. 2004. Ann Rev Psychol 55:23-50
Hanes & Schall (1996)
described neural activity
that looked like an
accumulator.
Activation
Linking propositions for decision making
0.0
They identified this
activity with form of
sequential sampling
models.
0.1
0.2
Time from stimulus (sec)
Linking propositions for decision making
RT = Decision time + Residual time
Residual time = Encoding time + Preparation time
Sequential sampling
Response preparation
Activation
Activation
Stimulus encoding
0.0
0.1
0.2
Time from stimulus (sec)
0.0
0.1
0.2
Time from stimulus (sec)
Countermanding task
N
O
S
T
O
P
S
I
G
N
A
L
T
r
i
a
l
s
R
e
a
c
t
i
o
n
T
i
m
e
S
T
O
P
S
I
G
N
A
L
T
r
i
a
l
s
C
A
N
C
E
L
L
E
D
S
t
o
p
S
i
g
n
a
l
D
e
l
a
y
N
O
N
C
A
N
C
E
L
L
E
D
Countermanding performance
Countermanding paradigm: Race model
Reaction Time
“GO”
NON-CANCELLED
CANCELLED
Stop Signal Delay
“GO”
“GO”
“STOP”
“STOP”
Logan, G.D. & Cowan, W.B. (1984) On the ability to inhibit thought and action: A theory of an act of control. Psychological Review
91:295-327.
Hanes DP and Schall JD (1995) Countermanding saccades in macaque.Visual Neuroscience 12:929-937
Saccades are produced by a distributed network
Frontal cortex
FEF
(DLPFC, ACC, SEF)
Parietal
Cortex (LIP)
Thalamus
Temporal
Cortex (TEO)
Visual Cortex
LGN
Basal Ganglia
SCi
SCs
Retina
Cerebellum
Saccade
RF
Munoz DP, Schall JD (2003) Concurrent distributed control of saccade initiation in the frontal eye field and superior colliculus. In The Oculomotor System: New Approaches
for Studying Sensorimotor Integration. Edited by WC Hall, AK Moschovakis. CRC Press, Boca Raton, FL. Pages 55-82.
Countermanding physiology
STOP SSRT
STOP SSRT
No stop trials
No stop trials
Non-canceled trials
Canceled trials
Hanes, D.P., W.F. Patterson, J.D. Schall (1998) The role of frontal eye field in
countermanding saccades: Visual, movement and fixation activity. Journal of
Neurophysiology 79:817-834.
Pare M, Hanes DP (2003) Controlled movement processing: superior colliculus
activity associated with countermanded saccades. Journal of Neuroscience
23:6480-6489.
Mapping the race model onto neural processes
1 - The race model of countermanding performance assumes
that the GO and the STOP processes have independent finish
times (Logan & Cowan, 1984).
2 – Saccades are produced by a network of interacting
neurons.
Paradox – How can a network of interacting neurons
produce behavior that looks like the outcome of race
between independent processes?
Mapping the race model onto neural processes
Explore properties of simple network of GO and STOP units.
daGO 
dt
da STOP 
dt


 GO   STOP  aSTOP 
 STOP   GO  aGO 


dt

dt

 GO
 STOP
Constrained by the characteristics of countermanding
behavior and by the form of activation of neurons
L.Boucher, G.D.Logan, T.J.Palmeri, J.D.Schall. An interactive race model of countermanding saccades. Program No. 72.10. 2003 Abstract Viewer/Itinerary Planner.
Complete independence
GO
STOP
L.Boucher, G.D.Logan, T.J.Palmeri, J.D.Schall. An interactive race model of countermanding saccades. Program No. 72.10. 2003 Abstract Viewer/Itinerary Planner.
Complete independence
GO
Reproduces countermanding behavior…
1.0
100%
b
probability(non-cancelled)
Observed
STOP
c
Model
0.5
50%
0.0
0%
50
100
150
Stop signal delay (ms)
200
250
200
300
400
Reaction time (ms)
L.Boucher, G.D.Logan, T.J.Palmeri, J.D.Schall. An interactive race model of countermanding saccades. Program No. 72.10. 2003 Abstract Viewer/Itinerary Planner.
Complete independence
… but does not produce correct activations.
Stop Signal
SSRT
Stop Signal
SSRT
GO
STOP
The GO process is
never interrupted!
L.Boucher, G.D.Logan, T.J.Palmeri, J.D.Schall. An interactive race model of countermanding saccades. Program No. 72.10. 2003 Abstract Viewer/Itinerary Planner.
Key insight – the inhibition of STOP on GO
cannot be uniform and instantaneous; it must
be late and potent
GO
STOP
Δt
Delayed potent STOP
GO
STOP
Δt
STOP
SSRT
Delayed potent STOP
GO
Reproduces countermanding behavior…
STOP
Δt
b
c
Probability (noncancelled)
1.0
100%
Observed
Model
50%
0.5
0%
0.0
50
100
150
Stop signal delay (ms)
200
250
200
300
Reaction time (ms)
400
Delayed potent STOP
… and reproduces neural activation
GO
STOP
Δt
The GO process is
not modulated in
non-canceled trials
The GO process is
modulated within SSRT
in canceled trials
Specific conclusions
Countermanding performance is produced by pool of
neurons the prepare movements (GO process) and pool of
neurons that interrupt preparation (STOP process).
The STOP process is composed of an early (afferent)
stochastic stage and a late potent interruption stage.
General conclusions
Redundant but distinct models cannot be distinguished
based on behavior data (Moore, 1956, in Automata Studies, ed. CE Shannon, J McCarthy.
Princeton Univ. Press)
Properties of neurons can distinguish between alternative
architectures
… but only if neurons instantiate the processes in question.
GO process identified with pool of “movement” neurons.
STOP process identified with pool of “movement inhibition”
neurons.
General conclusions continued
Stochastic response preparation process necessary to explain
countermanding performance.
If so, response preparation must be more or less stochastic during all
tasks.
Therefore, the proper form of response preparation variability must be
incorporated into sequential sampling models of perceptual or memory
decisions.
This and much other evidence indicates that RT is the expression of at
least two distinct but not necessarily discrete stages of processing –
encoding+categorization (decide that) and response preparation (decide
to).
General conclusions continued
"[Since] we cannot break up the reaction
into successive acts and obtain the time of
each act, of what use is the reaction time?"
– R.S. Woodworth (1938) in Experimental
Psychology [quoted in Luce (1986)]
It is possible now to determine the duration of intermediate stages with
invasive measures of neural states.
However, this depends on proper linking propositions.
Information about process durations and transitions is necessary to
elucidate how stimulus ambiguity, prior probability and reward history
influence choices.
An empirical basis for distinguishing between choosing and deciding
Anterior cingulate cortex
fMRI amplitude
Area MT
0%
100%
Motion strength
0%
100%
Motion strength
It is deciding when anterior cingulate cortex is engaged.
Rees et al. Nature Neuroscience 3, 716 - 723 (2000)
Parameter
Monkey C
Independent Interactive
Monkey A1
Independent Interactive
Monkey A2
Independent Interactive
μGO
4.62
4.64
5.49
5.42
5.12
4.99
σGO
18.53
18.22
23.11
22.81
22.91
22.84
μSTOP
12.11
11.56
27.42
21.45
27.60
23.08
σSTOP
13.22
18.22
140.60
140.97
140.90
141.07
βGO
0.00
0.00429
0.00
0.000265
0.00
0.0399
βSTOP
0.00
0.00694
0.00
0.00561
0.00
0.0399
DSTOP
1
71
27
15
27
50
χ2
cancel time
22.85
—
24.23
-18
89.74
—
91.16
-25
106.41
—
96.91
-23
STOPinterrupt
SSRT
—
103
11
102
—
77
35
77
—
76
10
85
Fixation cell activity from FEF & SC
Activation
(Spikes/sec)
Stop Signal
SSRT
Stop Signal
SSRT
100
0
200
400
Time from target (ms)
Hanes, D.P., W.F. Patterson, J.D. Schall (1998) The role of frontal eye field in
countermanding saccades: Visual, movement and fixation activity. Journal of
Neurophysiology 79:817-834.
400
200
0
Time from target (ms)
Pare M, Hanes DP (2003) Controlled movement processing: superior colliculus
activity associated with countermanded saccades. Journal of Neuroscience
23:6480-6489.